At present mobile traffic demands are increasing and will most likely exceed network capacities within the foreseeable future. One manner in which operators are fighting the increasing traffic demands is by utilizing so-called heterogeneous access networks. In heterogeneous access networks, mobile operators can move traffic from the cellular network, where the capacity constraints are most severe, to cheaper shorter-range wireless local area networks e.g. Wi-Fi. One problem with such complex mixes of cellular networks and wireless local area networks is the implementation of efficient policies to control the connectivity behavior of the user equipment when moving between the cellular network and the wireless local area network. The same problem also applies for the case when the user equipment is simultaneously connected to both cellular networks and wireless local area networks. In particular, there is little consistency between mechanisms used by e.g. Wi-Fi operators and those used by cellular operators to control for example network discovery, access or network selection, traffic steering or routing, traffic prioritization, user authentication, roaming capabilities and quality of service (QoS). At present, this also applies for the case when it is the same cellular operator providing the Wi-Fi related information. Roaming capabilities refers to the capabilities of the user equipment moving between the cellular network and the wireless local area network.
The information needed for efficient selection of radio access technology, RAT, is large and is stored partly in the Core Network and partly in the Radio Network, as illustrated in FIG. 1. Almost all Core network information is currently passed on to the radio access network, RAN, mainly when the user equipment, UE, becomes “RRC Connected” and when “Radio Bearers” are established. Examples of transferred information are: cooperating/allowed PLMNs (Public Land Mobile Network), subscription (allowed RATs, QoS rules), services (QoS rules). It can be noted that the information is usually ‘translated’. One example is the S1 ‘Handover Restriction List’, which is constructed based on allowed PLMNs and RATs. This information is passed over A/Gb, Iu and S1 interfaces. The RAN has information about e.g. available cells and radio technologies, quality of existing and potential radio links, cell loads including the mix of UEs with different QoS requirements present in different cells, etc. RAN makes a composite decision, taking both Core Network and Radio Network information into account.
In contrast, the current WLAN-3GPP integration method is UE-centric. The UE is provided with (mainly) Core Network information using the ANDSF method, as illustrated in FIG. 2. The content of this information is largely corresponding to the intra-3GPP information, which is passed over the A/Gb, Iu and S1 interfaces. However, the existing interfaces between Core Network and 3GPP RAN have no WLAN-related information at all. Upgrading the Core Network to provide such WLAN-related information may be considered complex, since it affects many nodes.
The so-called Access Network Discovery and Selection Function (ANDSF) provides the possibility to send different policies to the UE for access/network discovery and selection, and traffic steering/routing. The communication between the UE and the ANDSF server is defined as an IP-based S14-interface.
The communication between the UE and the ANDSF server typically consists of the following distinct information elements, access discovery information, inter-system mobility policies, and inter-system routing policies, wherein:                Access Discovery Information (ANDI) is used to provide access discovery information to the UE, which can assist the UE to discover available (3GPP and) non-3GPP access networks without the burden of continuous background scanning.        Inter-System Mobility Policies (ISMP) are policies which guide the UE to select the most preferable 3GPP or non-3GPP access. The ISMP are used for UEs that access a single access technology (3GPP or WLAN) at a time.        Inter-System Routing Policies (ISRP) are policies which guide the UE to select over which access a certain type of traffic or a certain APN shall be routed. The ISRP are used for UEs that access both 3GPP and WLAN simultaneously. FIG. 3 shows the Roaming Architecture for ANDSF (source is FIG. 4.8.1.1-2 in 3GPP TS 23.402).        
The above ANDI, ISMP and ISRP have been extended with additional policies in the later 3GPP releases, for example WLAN selection policy (WLANSP) and Inter-APN Routing Policies (IARP) policies.
FIG. 4 finally shows one exemplary mobile network architecture for the case of LTE/EPC and Wi-Fi.
The ANDSF or ANDSF settings or ANDSF policies can supply the UE with the parameters listed above, and thereby provide the UE with policies for the UE selection of RAT/RAN or radio access network selection and traffic steering. These policies are not as sophisticated as those of the cellular RAN/RAT and in particular they are not based on as fresh and detailed information on the RAN conditions as is available in the RAN/RAT.
Consequently, there is a need for methods and arrangements enabling improved control of radio access network selection and traffic steering for user equipment in heterogeneous communication systems.